Advertisements posted in Manhattan by the company that produces soft drink Mountain Dew liken Mayor Bloomberg’s proposed ban on large portions of soda to the prohibition era.

The New York City Board of Health on Thursday approved Mayor Michael Bloomberg’s controversial proposal to ban the sale of large sugary drinks in restaurants and other venues, a sweeping initiative that backers hope will reduce obesity and critics decry as government run amok.

Beginning March 12, the city will prohibit restaurants, mobile food carts, delis and concessions at movie theaters, stadiums or arenas from selling sugary drinks in cups or containers larger than 16 ounces. The city will begin fining sellers for violating the ban in mid-June.

The proposal passed by a vote of eight to zero, with one abstention, one absence and one vacancy on the board. Dr. Thomas Farley, the board’s chairman, called the vote “historic.”

Opponents said they are exploring all possible paths to prevent the new ban from taking effect next year, including the possibility of a legal challenge. Recent polls show a majority of city voters oppose the initiative.

Opponents have complained that the deck was stacked against them because every member of the board is appointed by the mayor. Adding to that perception, before the board voted, the administration delivered a 20-minute presentation rebutting the critics’ points.

After more than 38,000 oral and written comments, the administration proposed no changes to the initial proposal that was made public in May.

Joel Forman, a board member, said there is “overwhelming” evidence that obesity is a major health problem in the city and nation.

“I can’t imagine the board not acting,” he said. “I laud the proposal and I support it.”

Dr. Forman said he hopes the initiative will “spread nationally.”

Pamela Brier, a board member, described the initiative as “terrific” and said she wholeheartedly supported it.

“It’s hard to do – there are a lot of unhappy people,” she said, noting the criticism. She said she hopes the ban becomes the “new norm.”

Board member Lynne Richardson said she was skeptical at first but found the arguments for it “convincing” and “compelling.” She said the opponents engaged in “hyperbole that was stunning.”

Board member Susan Klitzman said the obesity problem in New York is patently obvious. “To not act would really be criminal.”

Deepthiman Gowda, a board member, called the initiative a “small” but “bold” and “exciting” step forward.

“The reality is we are in a crisis,” he said. “We need to act on this.”

Several of the board members stressed that they listened carefully to the public’s input, spending many hours reading the flood of comments both for and against.

The proposal is the latest high-profile initiative from Bloomberg, who has made public health a hallmark of his nearly 11-year tenure at the helm of the nation’s most populous city. In 2002, the mayor persuaded the City Council to approve a ban on cigarettes in restaurants and bars, a law that has since become widely popular in the city and adopted around the globe.

“Obesity is going to kill more people in the world his year than starvation,” Bloomberg said during an interview on MSNBC, just hours before the board’s vote.

The mayor has defended the ban, which he described Thursday as “portion control,” as an upfront way to alert consumers about the dangers of large sugary drinks. While the new rule bans the sale of sugary drinks in large cups, consumers may purchase as many drinks as they choose.

“I don’t think it’s government’s job to ban people from doing things with a handful of exceptions,” Bloomberg said. “But, generally, it’s government’s job to tell you the facts of what is bad for you and let you make your own decision.”

Bloomberg announced Thursday afternoon that the new Barclays Center, home of the Brooklyn Nets basketball team, will be the first major venue to voluntarily implement the ban.

Eliot Hoff, a spokesman for New Yorkers for Beverage Choices, a coalition of individuals, companies and groups opposed to the ban, said there was never any hope the Board of Health would reject the proposal because the mayor appointed all the members. More than 250,000 New Yorkers and 2,100 business owners have signed a petition against the ban because it is “arbitrary and restricts our choices,” Hoff said.

“We’re smart enough to make our own decisions about what to eat and drink,” said Hoff, adding that the ban goes “against the wishes of a majority of New Yorkers and we will not let that fact go unnoticed.”

A sugary drink is defined as any beverage sweetened with sugar or another caloric sweetener that contains more than 25 calories per 8 fluid ounces and contains less than 51% milk or milk substitute by volume as an ingredient. A diet soda, a milk shake or sweetened latte that is larger than 16 ounces wouldn’t be banned.

During the first three months after the ban takes effect, the city will inspect and inform sellers when they are not in compliance with the law. The city will allow a three-month grace period before it begins issuing notice of violations that are subject to fines.

More than half of New York City adults, or 58%, are overweight or obese, and nearly 40% of city public-school students in eighth grade or below are obese or overweight, according to the city.

During the mayor’s tenure, the Board of Health had required calorie counts to be posted on menu boards and banned the use of trans-fats in foods. The mayor’s administration also launched a major effort to limit the intake of salt.

Many of the initiatives, at first, were unpopular but public sentiment then changed, the mayor and other administration officials have pointed out. On Wednesday, for example, McDonald’s announced it will begin posting calorie counts on all its menus nationwide next week.

“Two or three years ago, they sued us to stop doing it in New York City,” the mayor said on Thursday. “I’ll rest my case, thank you.

In other business, the board also unanimously approved another controversial proposal that would require written consent from a parent or legal guardian when oral suction is performed during a baby boy’s circumcision. The written consent will require notification that the city advises against oral suction because of health risks, including the possibility of infecting the baby with herpes.

Dr. Forman said he thinks the board should consider even stronger action. “It’s crazy that we allow this to go on” he said.

Opponents, including some religious leaders, have called the requirement an infringement on their religious rights.